Kami of Celebration

Whenever a modified creature you control attacks, exile the top card of your library. You may play that card this turn. (Equipment, Auras you control, and counters are modifications.)
Whenever you cast a spell from exile, put a +1/+1 counter on target creature you control.

Harsh Mentor

Whenever an opponent activates an ability of an artifact, creature, or land on the battlefield, if it isn't a mana ability, this creature deals 2 damage to that player.

Iraxxa, Empress of Mars

Trample
Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.)
Paradox — Whenever you cast a spell from anywhere other than your hand, create a 2/2 red Alien Warrior creature token.

Sunspine Lynx

Players can't gain life.
Damage can't be prevented.
When this creature enters, it deals damage to each player equal to the number of nonbasic lands that player controls.

Memory Worm

Paradox — Whenever you cast a spell from anywhere other than your hand, this creature deals 2 damage to target player. That player discards a card, then draws a card. Put a +1/+1 counter on this creature.

Dire Fleet Daredevil

First strike
When this creature enters, exile target instant or sorcery card from an opponent's graveyard. You may cast it this turn, and mana of any type can be spent to cast that spell. If that spell would be put into a graveyard, exile it instead.